As flat-panel displays in which thin-film transistors driven by an active matrix method are used, a liquid crystal display, a plasma display, an organic EL display, an inorganic EL display and the like are known. In these flat-panel displays in which the thin-film transistors are used, wirings made of a metal film are formed to adhere to the surface of a glass substrate in a grid pattern, and thin-film transistors are provided at the intersections of the grid wirings made of the metal film.
As shown in a schematic vertical cross-sectional view of FIG. 3, it is well known that a thin-film transistor 110 includes a gate electrode film 2 of a pure copper film, a silicon nitride film 3, a Si semiconductor film 4, barrier films 5 of silicon oxide films, and electrode films 6 of pure copper films which are laminated in series on a surface of a glass substrate 1, and it is also known that the electrode films 6 consist of a drain electrode film of the pure copper film and a source electrode film of the pure copper film (both are indicated by “electrode films 6” in FIG. 3) which are partitioned by an isolation trench 8.
In a process of manufacturing the thin-film transistor 110 having such a laminated film structure, the isolation trench 8 that partitions the drain electrode film and the source electrode film is formed by wet etching and plasma etching. The surface of the Si semiconductor film 4 which is exposed at the bottom of the isolation trench 8 is in an extremely unstable state, and dangling bonds are increased therein. These dangling bonds become surface defects. The surface defects increase an off-current of the thin-film transistor. As a result, problems such as a decrease in the contrast of an LCD or a reduction in a viewing angle occur. In this manner, the surface of the Si semiconductor film 4 which is exposed at the bottom of the isolation trench 8 is in an unstable state where the occurrence of the above-mentioned problems cannot be avoided.
For this reason, it is known that hydrogen plasma processing is performed on the exposed surface of the Si semiconductor film 4 under the conditions where 100% of hydrogen gas is used, a hydrogen gas flow rate is in a range of 10 to 1000 SCCM, a hydrogen gas pressure is in a range of 10 to 500 Pa, an RF current density is in a range of 0.005 to 0.5 W/cm2, and a processing time is in a range of 1 to 60 minutes; and thereby, the dangling bonds of the surface of the Si semiconductor film 4 are bound to hydrogen atoms to stabilize the surface thereof (see Patent Document 1).
On the other hand, large-sized screens and high integration of various types of flat-panel displays have been developed remarkably in recent years, and with this development, much higher adhesive strength tends to be required between each of the laminated films included in the thin-film transistor 110. In the above-mentioned conventional thin-film transistor 110, high adhesive strength capable of sufficiently satisfying the above-mentioned requirement is secured between the glass substrate 1 and the gate electrode film 2 of the pure copper film, between the gate electrode film 2 and the silicon nitride film 3, between the silicon nitride film 3 and the Si semiconductor film 4, and between the Si semiconductor film 4 and the barrier film 5 of the silicon oxide film. However, the adhesive strength between the barrier film 5 of the silicon oxide film and the electrode films 6 of the pure copper films (the drain electrode film and the source electrode film which are partitioned by the isolation trench 8) is relatively low, and the adhesive strength therebetween is not high enough to satisfy the above-mentioned requirement.